Technical Field
The present invention relates to compounds for organic electric elements, organic electric elements comprising the same, and electronic devices thereof.
Background Art
In general, an organic light emitting phenomenon refers to a phenomenon in which electric energy is converted into light energy of an organic material. An organic electric element utilizing the organic light emitting phenomenon usually has a structure including an anode, a cathode, and an organic material layer interposed therebetween. In many cases, the organic material layer may have a multilayered structure including multiple layers made of different materials in order to improve the efficiency and stability of an organic electric element, and for example, may include a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, or the like.
A material used as an organic material layer in an organic electric element may be classified into a light emitting material and a charge transport material, for example, a hole injection material, a hole transport material, an electron transport material, an electron injection material, and the like according to its function.
Currently, the power consumption is required more and more as size of display becomes larger and larger in the portable display market. Therefore, the power consumption is an important factor in the portable display with a limited power source of the battery, and efficiency and life span issue also must be solved.
Efficiency, life span, driving voltage, and the like are correlated with each other. For example, if efficiency is increased, then driving voltage is relatively lowered, and the crystallization of an organic material due to Joule heating generated during operation is reduced as driving voltage is lowered, as a result of which life span shows a tendency to increase. However, efficiency cannot be maximized only by simply improving the organic material layer. This is because long life span and high efficiency can be simultaneously achieved when an optimal combination of energy levels and T1 values, inherent material properties (mobility, interfacial properties, etc.), and the like among the respective layers included in the organic material layer is given.
Recently, in order to solve the problem of light emission in the hole transporting layer of an organic electric element, it is preferable that an emission-auxiliary layer exists between the hole transport layer and the light emitting layer. It is necessary to develop different emission-auxiliary layer materials depending on the respective light emitting layers (R, G, B).
In general, electrons are transferred from the electron transport layer to the light emitting layer and holes are transferred from the hole transport layer to the light emitting layer to generate excitons by recombination.
However, since the material used for the hole transport layer has a low HOMO value, it has a low T1 value, which causes the exciton generated in the light emitting layer to be transferred to the hole transport layer. As a result, a charge unbalance occurs in the light emitting layer, and light emission occurs in the hole transport layer or at the interface of the hole transport layer, resulting in showing poor color purity, reduced efficiency, and low life span.
In addition, when a material having a high hole mobility is used to make a low driving voltage, the efficiency tends to decrease. This is because the hole mobility is faster than the electron mobility in a general organic electronic element, resulting in a charge unbalance in the light emitting layer. As a result, efficiency and life span are decreased.
Therefore, in order to solve the problems of the hole transport layer above, an emission-auxiliary layer material should have a hole mobility (hole mobility: within driving voltage range of the full device blue device) and a high T1 value (electron block) and a wide band gap. However, this cannot be achieved simply by the structural properties of the core of an emission-auxiliary layer material, but is possible when the combination of the core and sub-substituent properties of the material is combined. Accordingly, in order to improve the efficiency and life span of the organic electronic device, it is strongly required to develop an emission-auxiliary layer material having a high T1 value and a wide band gap.
That is, in order to sufficiently exhibit the excellent characteristics of the organic electronic device, a material forming the organic material layer, for example, a hole injection material, a hole transport material, a light emitting material, an electron transport material, an electron injection material, an emission-auxiliary layer material or the like, must be supported by a stable and efficient material. However, such a stable and efficient organic material layer material for an organic electric element has not yet been fully developed. Accordingly, there is a continuous need to develop new materials for an organic material layer, specifically, there are strong needs to develop materials for an emission-auxiliary layer.